The present invention relates to a printing plate and a printing process.
Various printing processes have been heretofore adopted. As typical instances, there can be mentioned offset printing, typography and gravure printing. According to the offset printing process, a planographic printing plate is used, an ink is supplied to the plate through many ink transfer rollers and a material to be printed is directly printed. According to the gravure printing process, an intaglio printing plate is used and a material to be printed is directly printed without using ink transfer rollers.
However, each of the above-mentioned printing processes has defects. More specifically, in the gravure printing process, since a material to be printed is directly printed without using ink transfer rollers, the structure of the printing machine is simple, but since an intaglio plate is used, a recess should ordinarily be formed according to the etching process and the plate-making process is complicated.
In the offset printing process, a planographic plate having no substantial convexity or concavity is used, and therefore, the plate-making process is simple and the plate can be easily attached to a plate cylinder. However, since a blanket plate cylinder has to be used and many ink transfer rollers have to be used, the structure of the printing mechanism is complicated. Although direct printing can be done by contacting a printing sheet directly with a planographic plate, the print quality is bad, and the process is fatally defective in that when a coarse surface printing sheet is used, the print quality is drastically degraded.
In the typography, since many ink transfer rollers have to be used, the structure of the printing machine is complicated and since a typographic printing plate has to be used, a convex part should be formed on the printing plate, the plate-making operation becomes complicated. Moreover, in the typography, since the contact area of a printing sheet to the plate differs according to the image density, and hence, pressure unevenness is readily caused, and a troublesome make ready operation should be carried out when the plate is attached to the cylinder.
The present invention has been completed to solve the foregoing problems involved in the conventional techniques, and it is therefore a primary object of the present invention to provide a printing plate and a printing process, in which the plate-making operation is easily accomplished, the structure of a printing machine is simplified and good printing can be performed even on a coarse surface printing sheet.